Hyphen

What Is a Hyphen?

A hyphen (-) is a punctuation mark that’s used to join words or parts of words. It’s not interchangeable with other types of dashes.

Use a hyphen in a compound modifier when the modifier comes before the word it’s modifying.

If you’re not sure whether a compound word has a hyphen or not, check your preferred dictionary.

Hyphen with Compound Modifiers: Two-Word Adjectives Before Nouns

Using hyphens to connect words is easy. Picking the right words to connect is a little harder. Let’s start with compound modifiers.

A compound modifier is made up of two words that work together to function like one adjective. When you connect words with the hyphen, you make it clear to readers that the words work together as a unit of meaning.

It’s recommended you don’t take down any load bearing walls when renovating.

In this sentence, it sounds like you shouldn’t take down any load that is holding up a wall. A hyphen should be inserted between load and bearing to make it clear that we’re talking about walls that are bearing a load.

It’s recommended you don’t take down any load-bearing walls when renovating.

This rock-hard cake is absolutely impossible to eat.

We’re looking for a dog-friendly hotel.

Generally, you need the hyphen only if the two words are functioning together as an adjective before the noun they’re describing. If the noun comes first, leave the hyphen out.

This wall is load bearing.

It’s impossible to eat this cake because it is rock hard.

Is this hotel dog friendly?

You also don’t need a hyphen when your modifier is made up of an adverb and an adjective.

Do you expect me to believe this clearly-impossible story?

Do you expect me to believe this clearly impossible story?

Hyphens With Participles

Compound modifiers that include present or past participles follow the same rules as any other compound modifier.

Hyphen With a Noun, Adjective Or Adverb and a Present Participle

When we combine a noun or adjective and a present participle (a word ending in ‑ing) to form a unit of meaning that describes another word, use a hyphen to make that unit of meaning clear.

There are some beautiful looking flowers in the garden.

Without the hyphen between beautiful and looking, your reader may stumble over the sentence. Perhaps there’s a new type of daisy called the “looking flower”?

There are some beautiful-looking flowers in the garden.

Fast-acting medication can be useful when one has a headache.

Don’t use a hyphen when the modifier comes after the noun it’s describing.

This medication is fast acting.

Don’t use a hyphen when you are combining an adverb and a participle.

The room was like a heavily-decorated chocolate box.

The room was like a heavily decorated chocolate box.

Hyphen in a Compound Expression With a Noun and Past Participle

Compound modifiers that contain a past participle also follow the same rules as any other compound modifier. Use a hyphen when the compound goes before the verb it modifies:

The municipal government is funding a community-based education system.

Wind-powered generators can be excellent sources of electricity.

Many veterinarians find meat-fed cats to be quite healthy.

A well-known local singer will perform tonight.

Don’t use a hyphen when the compound comes after the noun it describes.

The singer performing tonight is well known.

Hyphenated Compound Words

Hyphenated compound words are the ones (obviously) with a hyphen between the words. Over time, many hyphenated compounds become closed compounds—teen-ager became teenager for instance. Check a dictionary if you’re not sure whether to use a hyphen or not. Here are a few examples of common hyphenated compound words:

Mother-in-law

Master-at-arms

Editor-in-chief

Ten-year-old

Factory-made

Twelve-pack

Closed Compound Words

Hyphenated words tend to become closed compounds (single words with no hyphens) over time. Email instead of e-mail, for example, is increasingly common. If you aren’t sure whether a words is a closed compound or a hyphenated one, check your preferred dictionary.

Notebook

Superman

Waistcoat

Bookstore

Fireman

Open Compound Words

Open compounds are typically made up of two nouns that are used together to represent a single idea. “Open” means that there is a space between the two words and no hyphen. A good dictionary is the best place to check whether a compound is open or not.

Living room

Real estate

Dinner table

Coffee mug

Hyphens and Numbers

Numbers between twenty-one and ninety-nine should be hyphenated when they’re spelled out.

Fifty-six bottles of pop on the wall, fifty-six bottles of pop…

No, I won’t party “like it’s nineteen ninety-nine.”

I’ve got a hundred and twenty-two of these gizmos to sell.

Hyphen in Compound Adjective With Numbers

When numbers are used as the first part of a compound adjective, use a hyphen to connect them to the noun that follows them. This way, the reader knows that both words function like a unit to modify another noun. This applies whether the number is written in words or in digits.

The president of the company gave a 10-minute speech to the Board of Directors.

He is knowledgeable in thirteenth-century politics.

The boy threw a rock at the second-story window.

However, a hyphen is not required if the number is the second word in the compound adjective.

He is a victim of Type 2 diabetes.

This elevator doesn’t go down to Basement 3.

Hyphen In Compound Adjective With Fractions

When using a fraction (e.g. half or quarter) as part of a compound adjective, it should be hyphenated so the reader understands which fraction is modifying which noun.

I half-wanted to commit a felony.

A quarter-million dollars is still a large amount of money.

You’ll need one-third of a pound of flour and one egg.

That’s a half-baked idea if I ever heard one!

Hyphen With Prefixes: Ex-, Self-, All-

Use a hyphen with the prefix ex- (meaning former).

Don’t sit Adam next to Martha! She’s his ex-wife!

Though he no longer held an official position, the ex-mayor still attended all the town’s functions.

Use a hyphen with the reflexive prefix self-.

Lying on the floor beside the plant he had knocked over and chewed on, the cat looked extremely self-satisfied.

Do you want a self-serve or a full-serve gas station?

Make sure you don’t confuse the prefix self- with the noun self.

The self serves no other.

When using all as a prefix, add a hyphen.

It’s a bad leader who thinks of himself as all-powerful.

Hyphens with High or Low

When using high or low as part of a compound adjective, use a hyphen when the compound comes before the noun it’s modifying. Some examples of compound adjectives using high and low include high-level/low-level and high-impact/low-impact

Low-flying airplanes contribute to the noise pollution in the area.

This car runs best on high-octane gasoline.

Low-income families often face more stress than their higher-income counterparts.

A high-interest savings account is one of the best ways to save money.